After the manual power cycle reported by Francesco in his previous entry (67979), the WI CO2 laser appeared stable for some hours, until it switched off again and then restarted autonomously.

This happened at 17:38:30 UTC, after which the laser turned back on at 17:39:10 UTC.
A second event occurred at 17:51:50 UTC, with the laser restarting again at 17:52:50 UTC.

Cecilia briefly went to the TCS room to verify the hardware status, but did not observe anything abnormal.

Moreover, Francesco noticed that during every instability of the WI CO2 laser, the PR CHRoCC shows a simultaneous disturbance (see attached plot).
This correlation is quite puzzling, since the CHRoCC power supply is located on a completely different rack from the CO2 electronics.
For this night, there is not much we can do =(

The only anomaly noticed after a second investigation is a soft continuous crackling sound coming only from PR CHROCC K.E.R.T. Other identical devices do not produce this sound.

I am not sure whether this is relevant, but in correspondence with the power on/off events of the WI CO₂ laser and the glitches in the PR CHRoCC, simultaneous disturbances are visible on the UPS INF_CB_UPS1_RBT (see attached plot).

By looking at the time interval (Oct 19, 18:20–19:00 UTC) shown in Ilaria’s plot, we observed an increase in noise measured by the accelerometer and the episensor on the bench, coincident with the laser power on/off events (Figure 1). This correspondence is clearly visible around 18:22–18:28 UTC (Figure 2), and less pronounced between 18:40–18:43 UTC (Figure 3). During this period, the ITF was locked.
We also found coincidences in the UPS current and voltage monitors of phase T (Figure 4 - 5). Looking at other ENV sensors in the TCS room and in the CEB hall, no coincidences were observed.